180 NIADACE,£. 
den. The outer tunic approaches the leaves in structure as 
is pointed out by the fuscous teeth: this would seem to point 
out, that the disposition of the male flowersin the two species 
may vary. 
In Naias valisnerioides, which appears to vary in the ab- 
sence of a tunic to the stamina, the ovarium is anatropous, the 
foramen is in close relation with large lax cells, radiating 
somewhat from the short funicle. Of similar structure are 
cells radiating from the bottom of the stigmatic canal, where 
it opens into the ovary. And here I have seen traces of an 
excessively fine membrane, which may perhaps line the whole 
ovary, and which is conducting: similar membranous con- 
ducting tissue exists in Nelumbium. ; 
e pollen tubes are frequently seen passing down over the 
surface of the ovulum, they are generally lost sight of in the 
conducting tissue near the foramen, and are excessively fine. 
.. Even at an early period, the nucleus adheres to the second 
tegument. After fecundation, the inner tegument becomes 
very fine, and the nucleus becomes hollowed out along its 
axis, and filled or turgid with juice 
When the embryo is somewhat developed, the outer coat or 
layer of seed, (or testa) is cellular; the cells are large contain- 
ing green granules, the inner layer is beginning to be crusta- 
ceous and is composed of a single series of oblong irregular 
cells, highly punctate. The second tegumen is reduced to a 
membrano-cellular membrane, its apex is mammilliform acute, 
this adheres strongly to the apex of the nucleus, and gives it 
a radiate cellular appearance. 
The nucleary membrane is thin, tending to a leathery con- 
sistence, it is lined by a very fine cell, the membrane is com- 
posed of one series of cells, with minute granular matter. 
The embryo fills only a small part of the cavity, its funicle is 
composed of 3 cells, the terminal one is rounded and filled 
with more grumous contents, to this adheres an amorphous 
tubular substance. 
It is curious that in all these plants, the embryonary sac is 
